Process of excitation for induction-machines.



--rpgsfsffof BXGITATION POR INDUCTION MACHINES.

' APPLICATION FILED IBB. 5. 1904.

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l /7Zaa7'ce 172220110; wi/Fusano: l

MAR. 2o, 1906.

'PATENTBD MAR. 20.1906.

. M. LEBLANC. v PROCESS OFEXCITATION PCR INDUCTION MACHINES.`

APPLICATION FILED PEB. 5. 1904.-

'5 SHEETS-SHEET 2.

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No, 815,357. PATBNTBD MAR. 201, 190e. M. LEBLANC. PROCESS 0F EXGIT'ATION PoR INDUCTION MACHINES.' APPLIOAUON IIILIfD PEB.. 5. 1904.

5 SHEETS-SHEET 4.

No. 815,357., l

PATENTED MAE. 2o, 1906. f Y. M. LEBLANC. PROCESS OP'EXGITATION EUR INDUCTION MACHINES.

APPLIOA'IION FILED PES5. 1904.

5 SHEETS-SHEET 5.

Emmen n c sii-Arras 'PATENT orrion.

MAURICE LEBLANC; or rARisQraANen, Assienoa 'ro wEsriNeHoUsE l annorinc SYLVANiA.

eno-cess oF Exc-:Harlow No. :315,357l

& MANUFACTURING COh'llANY, A CORPORATION OI" PENN- Fon INDuCTwN-MACHINES.

Specification of Letters Patent. v l Patented March 20, 1906.

v Originalapplicaticii filed ln'ua'r'y 28, 1903, Serial No.,140,933. Divided and this application iiled February 5, 1904. Serial No. 192,226.

To all whomI lit 11m/y conce/'71,:

Be it known thatI, MAURICE LEBLANC, a.

citizen of the Republic of France, and a resident' ofl Paris,- France, have invented a certain' new and useful Im roveinent in Processcs of Excitation for nduction-Machines,

' Y of which the following is a'speciication.

It is now well understood in the art thatval-` ternating-current induction-machines, or, as

they are otherwise known, asynchronous machines, wheiilocated in branches derived from a mam line fedby 4an alternating generator o erate as motors when rotating with a'speed )elow synchronisin and aslgenerators when driven at as In .eithercase the inducing' member or primary is traversed by currents of line frequen'cy andthe induced member or second iggrees behind what may be called the ary by currents of slip frequency. What is more whether the asynchronous machine op crates as a motor or as a generator it takes from the line the currents necessary to inagnetize it-that is to say, it takes from the line the wattless current which lags ninetyl deenergy-current. Expressing the matter ina different way, the currents 'in the several members of asynchronous machines tend to lag owing to thefact that they are obliged to generate a in agnetic field. TheI resultant current in either of these two circuits ma therefore be lconsidered as compounded rom an energy-current in phase withthe electromo' tive force and a Wattless current ninety degrees behind it. This wattless current,which is due to the self-induction of the machine and which causes the electroniotive force and the resultant current to be out of phase with cach other, gives rise to one of the principal defects of asynchronous machines.v

' One f the objects of the'present invention is to remove this defect in anexpeditious Way by impressing upon either member tof the asynchronous machine an alternating wave eed above synchronismj wave of'electroinotive-force which E reduce the apparent self-induction ofthe machine to zero or, vwhat is the same thing, to

Looked at in anotherfvvay, the exciter which currents to the asynchronous machines in'- ,thern Since, however, it is far more efficient to impress this advanced wave of alternating electroinotive force upon the induced member of the asynchronous machine, which is traversed by currents of the comparatively' low slip frequency, than upon the inducin the higher line frequency,this lnvention will be more specifically describedunder the aspect that my exciter which generates the advanced Wave of alternating electromo'tive force is appliedto tlie'induced member ofthe asynchronous machine. So, too, for the sake of clearness my invention will be described as vmore specifically applied to a three -phase alternating machine, although it will manifestly operate with any other number of phases.

Another object ofv my invention is to impress upon the secondary or induced member of the asynchronous machine an electromehundred andl eighty degrees with reference to the secondary currents.

parent positive or negative ohmic resistance which will act to increase or decrease the effective secondary' resistance of the asynchronous machine. lVlien the asynchronous niachine acts as a motor, the addition of a negative resistance will reduce the slip frequency, and if the added apparent negative resistance is e( ual to the internal secondary resistance the induction-motor may be"o erated at a constant synchronous speed w ile still acting as an inductionmachine` `By making the added apparent negative resistance greater than the internal secondary resistance the induction-motor will increase in speed with increase of load. In the case of inductionfgenerators the apparent negative resistance added to the induced member will also decrease thesupor the generator, .so that if the total apparent i secondaryresistance is zero niake it operate witlr'v unitpower factor.-

Such electrorno' tivey force will produce the eifect of an ap-` I have devised for executing my process furnishes the necessary Wattless or magnetizing stead of requiring line currents .to furnish-- member, which is traversed by currents o tive force in phase with or depliased by one roo drop in frequency in Ic5 the inductiongeiieiator will opei'ate at constant synchrol ondarycireuit of the asynchronous inaciiincs nous frequency. If the. total apparent secondary resistance is made negative, we will have an induction-generator in which the frequency will increase with increase of load or will maintain constant frequency with a speed dropping with increase of load.

Still another object of iny invention is to use a synchronous alternating-current generator, commonly called an alternator, in conjunction with a number of induction-generators in such a. manner that the alternator fixes the frequency and potential of the currents which the induetion-generators shall furnish. This so far is a well-known arrangement; but in accordance with my process I so regulate the action that the alternator will drop in speed with increase of load, whereas the induction-generators will maintain a practically const-ant speed under variations of load. An increasing load on the system will thus produce an increased slip on the induction-macliines, so that they may carry greater loads, and the total load will be more uniforinly distributed. At the saine time I add one of my exciteis to iiic secoiularyef each ot" the induction-generators, which exciter thus furnishes to these secondaries the necessary wattless or inagnetizing currents. By then properly varying the magnitude of the exciting-currents furnished to the induction-seconda-ries under different loads by simultaneously varying the speeds at which the exciters are driven these exciters will furnish all the wattless currents which the inductiongenerators require, and there will be no watt-` less currents passing between the alternator and the induction-niacliines.

Coming now to the apparatus which I have devised for carrying out the processes above indicated, and more especially to the apparatus which I have devised for executing the process by which the effect of an apparent negative reactance 'or an apparent negative resistance is added to the induced or secondary members of the asynchronous machines, I may say that Hutin and Leblanc in their United States Patent No. 613,204, of October 25, 1898, have described a system of excita-- tion in which they impress upon the induced members of asynchronous machines an advanced wave of electroinotive force of a character which neutralizes the self-induction of the machine-that is to say, of a character which furnishes the wattless currents necessar for its magnetization. Restricting inysel for the Sallie of clearness of description to the case in which the currents i, t, i., in the secondary or induced members are triphase, I may say that Hutin and Leblanc in the patent referred to provide as exciters three current-generators of the direct-current type, having coininutators and brushes resting thereon. The armature-circuit of the first exciter is connected to that lead of the secwhich carries the current ir The armaturecircuit of the second exciter is connected to the lead of the asynchronous secondarywhich carries i2, and the armatiie-,cii'ciiitl of the third exciter is connected to the lead of the asynchronous secondary which carries the current i3; but thefield of the first rcxcitei is by separate held-windings and a proper system of interconnection, in effect excited by a current ,*iw The field-circuit of the second exciterl is energized by a current of i3 il, and the field-circuit of the third exciter is excited by a current of i, i2. It is rigorously proved in the specification of Patent Xo. 613,204 by means of a vector-diagram that three generators of the direct-current type so connected and excited will sup ly to the asynchronous machine currents ol) a proper phase to neutralize its self-inductionthat is, to furnish to the asynchronous niachine the currents proper for its magnetization without requiring the machine to call upon the line for such current. This proof need not be repeated here; but in Patent No. 613,201 there are required as many excitergenerators of the direct-current type as there are phases to the secondary of the asyncliro` nous machine, and, furthermore, the fields of these generators of the direct-curi'ent type are energized by separate field-windings, Now I have discovered that4 I n'iay-substitute for the number of separate exciters of the patent in question a single exciter and yetat-tain the same result formerly effect-ed by ioo the multiplicity of exciters. T iis new single exciter is also a generator of the direct-current type whose rotor-armature is supplied with depliased windings of such character that the armature itsel furnishes the proper m5 Ymagnetic flux to its stator-field, so that the necessity for a separate field-winding on the stator of the exciter is dispensed wit i. Besides, by adding to the field of my new exciter a winding iii series with lthe exciter-ar no mature and ol' a character to produce a magnetic llux having an axis at right angles to the brushes of the exciter-armature l have discovered that I can cause the new exciter to supply to the secondary of the asynchronous ina-chine an elcctromotivc force in oppositioii to the voltage inserted by the currents in the asynchronous secondary, thus giving the effect of a negative ohmic resistance added to this secondary.

In the drawings, Figure 1 is a diagram ofthe system of excitation of Patent No. 613,204. Fig. 2 is a diagram showing the magnetic. axes and the distribution of currents on the rotorarinature of my new exciter. Fig. 3 is a dia- 125 grain showing the dephased armature-windJ ings of my new exciter and the distribution of currents thereon. Fig. 4 shows an end elevation of the rotor-armature and stator-field of niy new exciter. Fig. 5 shows a side eleva- 13o 65 ari'nature impresses upon tion of this new exciter. Fig. shows'an'ele- I cuit to' which itis connected an. electronicva tion ofthe sa ine. Fig. 7-shows a diagram of the starting-rheostats to be used with my exciter. Fig. S shows an alternatorand coperating induction-machines with my exciters applied to the latter. Fig. 9 shows the stator of my exciter provided with. a separatev fieldwiiidiiig for 'diminishing the apparent resistance ofthe asynchronous machine. Fig. 10 1o shows one of a number of like bobbins with which the armature of .my exciter is wound, y and Fig. 11 shows a diagram of the system of interconnecting the dephased armature- .windings of my exciter.

In Fig- 1 I have indicated the system of excitation of Patent No. 613,204.l I have indicated at the center of this figure the three triphase secondary circuits of the asynchronous machine which is to have its self-inzo duction neutralized. At threeA equally-displaced points-aroundl the center of the figure have indicated4 three exciter-generators of the direct-current type having rotor-armatures with brushes restin f thereonv and havz5 ing stator-fields. It is to e understood'that these rotor-armatures are supplied with com- `.rnutators and armature-windings, as is common indirect-'current generators, and it is furthermore to be understood that the stator- 3o field structures are laminated and built in the usual way. All this will be plain from the prior patent.

and S3 of the single asynchronous machine 3 5 which is to -be regulated, although I lmight have shown a delta connection. 'The secondary circuit S is connected to oneof the brushesresting on the armature B of the first ofthe exciter-generators of the direct- 4o current type. Continuin to trace this circuit, it. passes through t e armature justv s ecified, then in a given direction through t e field-coil C2 of the second exciter, and finallyin the op osite' direction through the field-coil Da of tii tral point or circle O. Tracing similar circuits for the asynchronous secondary circuits Si and Si', it is readily seen that if the asynchronousv secondary circuits S S2 S3 carry 5o currents i, i, 'im respectively, the fii'st exciter' has its armature.connected to the circiiit carrying a current i, and has its field traversed by a current i, i3, and that the second exciter has its armature connected to the circuit carrying a current i,3 and its field traversed by a current i3 L It is finally seen that the armature of the third exciter is connected to a circuit carrying a current is traversed by a current "il i2, Each field va- 6o `ries periodically with the common frequency .of the currents 'il i, i, in the secondary circuits. Now,y as stated above, it is provediiithey prior patent that with such asystem of excitation as has just been described each exciterthat secondary cir- I have assumed a Y connec-' tion for the three secondary circuits S', S2,A

e third exciter to the neuand that its field isv tive lorcey which has the saine Vfrequency as 'that of the current in the secondary circuitsl afact readily ap parent--aiidth at the phase ol i this impressed electroinotive force thus fui'- nished by each,exciter-armature is ninety dechronous secondary circuit to which it is connected. In order to bring about this desired phase relation, lit it seen that each exciter-ai"- niature has been connected to its'correspond- .ing asynchronous secondary crcuit. and that portional to the difference of. the currents flowing in the other asynchronous circuits.

first to the second exciter-brushes-that is, between thethird air of .brushes shall. be connected to the tiird secondary circuit of the asynchronous machine. armature-circuit between the first pair of brushes must cut, across a magnetic field genference in the currents which fiow in the secnetfic/ field having an intensity proportional to the difference of the currents which flow in the third and first secondary circuits, respectively. Finally, the armature-windings between the third pair of brushes must cut a magnetic field having anlii'itensity proportional to the difference of the currents which flow in the first and second secondary circuits, respectively,

devise a single exciter-generator of the directcurrent type with, say, three equally-spaced brushes, so that the armature-winding benected to the corresponding asynchronous secondary circuit and so that, -furtheriiiore, the armature-winding between this given pairof brushes shall cutacross ainagnetic field proportional to the difference inthe curary circuits, which magnetic field. is generated bythe action of the armature-winding itself..

grees in advance of the current in that ,asyneach armature has been rotated to cutv across. a magnetic field having a flux intensity pro- 1 Thereupon the ond and thevthird secondary circuits, respectively. ,The armature-winding between their" secondrpair of brushes must cut across a mage'v` More briefly stated, the problem which I have set myself to solve is to tween a given pair of brushes shall be ,con-

' The problem which I have 'set myself to v and so that the armature-circuit from the IOO erated by the armature-windings themselves, i having an intensity proportional to the dif- IZO rents in the two other asynchronous second` f currents in each secondary circuit.

If I succeed in devising a single lexciter which shall fulfil these conditions, it will now Vbe evident that I may connect` the three brushes of this exciter to the'secondary circuits of the' asynchronous machine. Upon rotating the exciter its several armature-circuits will each cut across a magnetic field which varies periodically and at the saine frequency as that of the secondary currents. These fields will each have an intensity to impress upon each exciter-armature circuit in itsy rotation an electroinotive force ofthe proper phase to diminish or neutralize the self-induction of the Put in other Words, the exciter will furnish some or all of the magnetization-currentsfor the asynchronous machine which -may'now operate Wi th unit-power factor.

I have indicated in Fig. 11 an armature- Winding which fulfils the conditions I have just proposed, it being understood that the rotary armature is to be used in connection with astator-field of the kind indicated at P in Fig. 4, having six notches equally displaced on its inner surface, but having no field-winding for the pur ose of producing the type of held Which I lave described at length above. So far as I am now concerned the stator structure simply serves as a path of small magnetic reluctance to close the magnetic circuits generated by the armature.

sections.

I have indicated in Fig. 10 one of the numeious similar bobbins A1, which I employ and place upon the armature structure to constitute its armature-winding. These bobbins may be Wound with any desired number of turns upon a mandrel of proper shape,

Aand when finished one Wire` of entrance will pass into the bobbins and one'wiie of exit will pass out of the bobbin. supposing at first, for the sake of simplicity, that the bo-dv of the armature, which will be laminated, carries six equally-displaced grooves 1, 1 3, 25, 37, L19, and G1, and suppose, furthermore, that the oominutator had six corresponding I place six of the bobbins A, iii thesix grooves just referred to in the following manner: I take the 'first bobbin and place one of its straight sides in the groove 1 and its opposite parallel side in the groove 37. yI place one straight side of the second bobbin in the groove 13 andl its opposite parallel side in the ciametrically opposite bins; but I arrange matters so that any bobbin which has one of its straight sides at the top of one groove has its opposite straight side in the bottom of the diametrically opposite groove, this being convenient for the purpose of keeping track of the direction of' currents in the various wires. I now interconneet the ingoiiig and outgoing Wires of the sixv bobbiiis and the six coiniiiutator-plates Shoa-n in F ig. 11 in a manner indicated with suflicient clearness in the drawings. If We 'apply to the current i2, flowing from the brush III to the brush I, and to the current is, flowing from the brush I to the brush II. The outer portions of the grooves 1 and 13 are thus seen to be traversed by a current il, the outer portions of the grooves 25 37 are traversed y a current i2, and the outer portions of the grooves 49 61 are traversed by a current fig. These currents all flow in a given direction. The inner portions of the grooves 37 49 are traversed by a current il, the inner portions of the grooves 61 1 are traversed by a current i2, and the inner portions of the grooves 13 25 are traversed by a current i3.'

These currents last mentioned in the inner portions of the grooves all flow in a direction opposite to that of the currents first inentioned iii the outer art of the grooves'. If now we consider a arger number of armature-groovessayseventy-two and a corresponding number of commutetor-sections, it will be evident from what has been said, at least to any one who is skilled in the art of Winding armatures, that I can cause the current 111' to pass in a given direction through the outer windings in the grooves 1Ato 24, inclusive, that I can cause the current i2 to pass in the saine direction in the outer portion of the windings in the grooves 25 to 48, inclusive, and that I can cause the current i, to pass still in the. saine direction in the outer portions of the grooves 49 to 72, inclusive. It will, furthermore, be evident that at the saine time a current fi, will flow in a direction opposite to that just referred to in the windi; gs in the bottom portions of the grooves 37 to 60, inclusive, that the current 'L2 will flow in this opposite direction iii the bottom poi'- tion of the grooves 61 to 12, inclusive, and that the current i3 will also flow in this opposite direction in the windings in the bottom portions of the grooves 13 to 36, inclusive.

5 If now we consider Fig. 3, We shall find that I groove 49, and so on for the other four bobhave attempt-ed to indicate the outer armature-winding, which has just been described, by the zigzag circle H and the inner armature winding by the zigzag circle J. I have placed alongside of that portion of the winding H IOO IIS

which runs from the brush II` to the brush n III a curved arrow (marked. i,) to indicate that a current i, is traversing this portion of the arinature-Winding. So, too, I have placed a curved arrow i2 alongside of that portion of the outer armature-winding H which runs from the brush III to the brush Ito indicate i flowing in the' outer armature-windings have i which seen to' be the proper value for the between the first pairof brushes, which we their outer 'armature-windings traversed by circuits between the first pair of brushes-that that this portion of the varmature 'winding is .traversed bya current i2. Then I have placed a curved arrow i3 alongsidev oftliat portion of the outer armature# winding II which rims from the brush I to the brush II to indicate that this portionofl the outer ar-y mature-winding is traversed by acurrent 91,. '.lhe curved arrows placed on the inside of the inner armature-winding Jin Fig. 3 indicate that the portions of the inner armature-windings adjacent to the arrows are respectively traversed by currents il, i2, and f. Ii we compare Fig. 3 with Fig. 11 under the assumption that the arinaturewinding has been extended to cover, say, seventy two grooves in the manner above specifically described,"it will be found that the currents been properly represented by the three curved arrows, each one hundred and twenty degrees long, placed ron the outside of the cir cle Hand that the currents flowing in the inner armature-windings Vhave been properly represented by the three curved arrows, each one hundred and twenty degrees long, placed on theinside of the circle J in Fig. 3. Pursuing the subject still further, it is found that allthe grooves from 1 to 12, inclusive, have currents I1in .a given direction and their in.-

z'if-A sin. 2 7i a t; z'rzAsin. 2 Yr where ail-is the frequency. The intensity of the magnetic fiux along the line F/ in Fig. 2

be concentrated at the center of each group. In order to iind the magnetizing efl'ect ol` the armature-windings along the axis F', we

purpose I have in view. Similarly we can calculate that the intensity of magnetization along the arrow F? is proportional to i3-i1, and thatzthe intensity of the magnetization along the arrow F3 is proportional to i, 112.

Let us now again consider the armatureis, between the brush II and the brush III. Recalling the mode'of winding of this-armature-circuit by referenceto Fig.` l1 it will be remembered to consist. of a number of loops displaced Varound the circumference of the rmature' through one hundred and twenty degreesL-that is to say, considering as a loop the structure A of Fig. 10, which consist-s of a wire carrying a current in-a given direction, together with a diam etricallyopposite wirefcarrying current in theop'posite d irection, it is seen that' the armature-circuit assume to be connected to the-secondary ciriier armature-windings traversed byfcurrent's y i2 going inv the opposite direction-'fthat is to say, each of the grooves :from 1 to 12, inclurent fi, t2. Similarly, the grooves 113`to24,i1 i'1 elusive, arel each found in effect, to be travy `ersed by currents t', i2," the grooves 25 to 3`6,`

inclusive, by currents i., i3; tlielgrooves 37 to 48, inclusive, by currents/2% the grooves 49 to 60, inclusive, by currents i, il, and the y grooves 61 to 72, inclusive, by currents 3712.

This vI have attempted to indicate by the sixv curved arrows,each sixty degrees long, on the outside of Fig. 3, these six arrows corresponding to the six groups ol'arinature-cir# cuits. It is to be understood that each lof these arrows is marked with the amount ofl current which traverses each or any ofthe armature-grooves in that portion of the circumference along which they extend. Y y

Let us now assume that the exciter-brushes are connected to a source of triphase current,

and since this invention, as above pointed out, isparticularly applicable to 'asynchronous machines let us assume that the exciterbrushes are connected to the three secondary circuits of such an asynchronous machine,

although, as will be apparent,they mighty also be connected to theprimary circuits. A.

Manii'estly we may take must manifestly project these armaturewindings upon a diametrical planeperpend icular to the axis F. Designating. by N the number of turns in each group of` 0011-" ductorsthe intensityof magnetization along the arrow F is equal to cuit carrying the current il, ris composedof twenty-four loops lying in the vdiametrically opposite pairs of groovesl to 37 `to 24 to 60, inclusive; but the magnetic flux F', whosey intensity is proportional tot2 i3, is seen to lie at the very center of this group of armatureroo' circuits passing from the .brush II to the/ I brush III, so that in lthe rotation of the ar-` mature this group oi armature-windings cuts straight across this magnetic flux, whereby, as has been above explained,'there is gener-` ated in this armature-winding anelectromotive force having the'same frequency as that y y of the currents t, t, i3 and having a phase IIO cut, it will be seen that the first problem y which I have proposed to myself has been solved. I need merely add that this solution does not require an exciter of any considerable power or size and that there is but little sparking in its brushes.

I may here call attention to the fact that the periodic variations of the field F due to the variation of the current i, t, develops no electromotive force in the circuit which passes from the brush II to' the brush III on the assumption that the armature is stationary. It is the rotation of the armature across this field which develops the leading electromotive force between the brushes, the magnitude of which electromotive force is proportional to the speed of rotation of the armature. If, however, we consider the magnetic field developed by the armaturewindingsat right angles to the axis F', which calculation shows to be proportional to Ni, we see that, although the electromotive force developed between the brushes II and III by the rotation of the armature with relation to this field Nt, is manifestly zero, yet the periodic variations of the field Nfl, due to the variations of the currents il, under the assumption that the armature is stationary, acts to develop between the brushes II and III an electromotive force of a magnitude proportional to the frequency a of the current f,. This electromotive force is of a kind to increase the self-induction of the asynchronous secondary circuit to which it is connected. Since, however, I always make the revolutions per second of the eX- citer-armature much greater than the frequency per second of the alternating-currentcircuit to which it is connected, it will be seen that the disturbing electromotive force due to the magnetization N111, the intensity of which is proportional to a, may be disregarded with reference to the leading electromotive force, the intensity of which is proportional to the armature speed. It is now seen why I preferably connect my exciter to the-secondary circuits of theasynchronous machine. These being in normal operation traversed by currents of the low-slip frequency I may readily rotate my armature at ten times this speed. If the exciterwere connected to the primary of the asynchronous machine carrying currents of line frequency at, say, sixty cycles, the speed of my exciter-armature might readily have to be eX- cessive.

I have been describing an apparatus for executing the process which produces the effect of a negative reactance in alternatingcurrent circuits, and while this process may manifestly be applied to alternatingcurrent circuits connected with any desired source of alternating or multiphased currents it will yet be seen to be peculiarly applicable to the secondary circuits of asynchronous machines, whether used as generators or as motors, and I have therefore, to avoid the use of alternatives and complicated descriptive terms, described my invention above in its a plication to the secondari' circuits of async ronous machines. i

I have now to describe the apparatus which I have devised forexecuting the process in accordance with which the effect of an added negative ohniic resistance is produced in that ty e of an alternating-current circuit wliicn is ound in the secondary of an asynchronous machine. To this end I simply arrange on the stator of my exciter separate field-windings, each in series with an armature-brush and each arranged to produce a magnetization at right angles to the diametrical line of the armature-brush to which it is connected. Since each field-winding is in seri es with the armature-brush, the variations of the field produced by it will have the same phase as the 'current in the brush. The rotation of the armature in the field will thus produce an electromotive force of the same phase as the current in the brushes or dephased by one hundred and eighty degrees with respect thereto, according to the direction which is given to the field-winding. To produce the effect of a negative resistance in the secondary circuit, the exciter should consume in the secondary an electi'oinotive force in opposition with the secondary current. This means that the exciter induces 'in the secondary an electromotive force in opposition with the voltage effect of or the voltage inserted by the secondary current.

In Fig. 9 I have shown a bobbin A located in those diametrically opposite Grooves of the stator which are in line with the brush I. This bobbin has Ithe wire of exit connected t0 the brush I and its wire of entry located at the point 1. Manifestly this bobbin Will produce a magnetization at right anglesto the diametrica direction of the brush I. Simi- 'larly I have placed a bobbin A in the two diametrically opposite grooves of the stator which are in line with the brush II, and a third bobbin A in the two diametrcally op.

connected to the incoming terminals 1 2 3 of the bobbins A A A. From what has been said it is evident that by absorbing or by spending work on the shaft of the exciter we can artificially increase vor diminish the apparent effective ohmic resistance of the alternating-current circuits or of the secondary circuits of the asynchronous machine, just as I have heretofore shown how to I .rtificially vary their coefficient of' self-induction.

By adding a field similar to `'that shown at IOO IIO

IIS

is, the sllp freq uency-may easily be taken as degrees `from thev field-winding A A itself j to Y. .or y,substract yitself from that provduc'edljy theirotor; but as this isa matter whlch y11s.wellunderstood in the art no spe-` cific description of itis needed. y y

Iy have assumedfn the preceding description that theexciter is bipolar; vbut then there may be any number of cles, it being sufficient to multiply thenum er of notches formed in the stator in proportion to the number of poles. There 1s no relation `between the number of oles of the exciter and those of the induction-machine which it must excite, nor is there any necessary relation between the rotary speeds of these two mahines, although it is advantageous to rotate the exciter as fast as possible. y

If it ybe desired to avoid intermediate gearing and. to drive the exciter from the samehsourceof mechanical power as the ind uction-machine, we only mount the exciter on the shaft of the inductioil-machine, as is shown in Figs. .5 and 6, where 1 is the induction-machine and 2 the exciter. The journal-box which is opposite the exciter may be lubricated by an oiler T, and a lug U may be used in withdrawing the oil rom the journal-box. The induction-machine is of the usual construction, and the r.const-ruction of the exciter has been sufficiently described heretofore. I need merely add` that eachfof the rods w y e bears a brush which rests on the commutator of the exciter and another brush electrically connected with the first which bears on one of the three sliprings connected to terminals of the secondary circuits'of Vthe, asynchronous machine In this manner thetermnals of the secondary circuits of the asynchronous machines are respectively connected to the exciter-brushes.

In the prece ing description I have assumed that the frequency of the currents developed in the secondary circuits and impressed upon the exciter-brushes is small as compared with thelre uehcyof rotationof the exciter.` Now when t 1e asynchronous machine has attained its normal speed the frequency of the current inthe secondary circuit of this machine-that low as two. It will manifestly be quite possible then to rotate the exciter at ten times this speed If, however, we should connecten exciter' of the kind I have described and rotating at the frequency twenty with the`secondary circuits of an asynchronous machine when this is starting in. operation 'it will befound that the sli frequency of the second ary currents may lie readily as greatas or even greater than the frequency of rotation o1 the exciter-armature. This exciter instead of reducing the self-induction of the asynchronousmachines would then actually act to increase it.y This follows from what has l current tothe line, so'that the"` amount ofthe y `:tothe ,stator strueture,- but shifted levers 6.7 Sito the right. Ail t "been said in aprevious paragraph with relation'tofthose disturbing electromotive -forces `which are proportional to 'it he frequency@ of the` secondary currents.` One means of overcomingthisditticultywould be to increase the speed of rotation of the exciter so as always. n

rotation much greater than tl1elfi'ef`|ueney of machine even at starting. Vev mghtthen `to have `the"frequency of the exciter-armature reduce the exciterarmature vspeedv thei asynchronous machine approximates normal speed and the slip frequency 'of its secondary currents is diminished; but this would be anv inconvenient if not an impract cable `proce`" dure. I Atherefore prefer to' us Vyin starting" the asynchronous machine anyc nunon type of starting-rheostats, such as those shown in Fig' 7. Ihesecondary circuits' of the asynf chronous ,machine are assumed toterminate at the extremities 10 11 12 of theconductinglevers 6 l7 S, eonnectedby"the insulating cross-bar S). These levers"` rest on fthe seg-- ments 3 4 5, respectiyelyI -ofrheostats 1314 15, the end terminals 17 18 1S) otwhlch are connected to the short-circuiting'bar 16. To

each rheostat is added a terminal20 21 '22,. I each connected with one of.the"threebrushes of the exciter-armatures f. i.

` W hen the asynchronous mach-:1w:isstartL through a maximum amount if rcsistz'lnce` As the speed increases this r( ,stance Ais diminished by throwing the .u per-ends of the isis the usual practice. 'When they inductionfmachine! has finally attained its normal speed, the levers 6 i lng up, its secondary Acircuits will pass fr:

IOO

7 S. are thrown on the termiinils-20 21 22,*re-

spectively, so that each Sew-lidar `circuit 1() v 11 12 is connected to its approprif te exciterbrush through the levers 6- 7' lS and the ter-4 minals 20 21 22. 'w

I yhave in the preceding .description attempted to drawno distinction between the asynchronous machine operating Vasa motor4v or operating as a generator, since my invention is applicable in either case ;,but when the y asynchronous machine 1s used as amotor it j will generally be inconvenient to regulatethe action of the exciter associated? therewith under variations of load of tlieaSynchrOnus or I therefore in tlnscase def induction n'sotor. sign my exciter so as t'o/giye unit'powerfad tor tothe induction-motor t'o which it is connected when this operatesat" mean load." Since matters varyy slowly'lin the neighbor hood of mean load, thispower factor willal-r ways remain quite nearunity lwhen the n1o`l tor-load varies. duction-motors fed'lfrom'the same line, each associated with onev of my exciters, which motors work on different loads,"some of'the'se If there are" a number Vof in` 'f motors will' take wattless current from' then`y lline and other motors -will furnishf'wattless 'rect-.current generator XVII.

wattle'ss currents whichathe central station has to furnish is practically fz'ero but when my exciters are'to beusedin connection with induction-generators'itwill be desirable to A vary their action-that is, to vary their speed of rotation-during the variation of load. I

. connect its other two brushes through a rheostat XIX, with thecircuit XV fed by the dirlhe rheostat XIX may be used to keep the voltage at the terminals of the synchronous alternator VII constant; but I much prefer to usethe voltage-regulator of my application, Serial No.

y137,933, filed January 5, 1903.

The synchronous generator VII is driven yby'a steam or hydraulic motor provided with a regulator which is` not very Sensitive, and the induction-generators IV, V, and VI are driven by steam or hydraulic motors provided with sensitive regulators which maintain their speed as constant as possible. At

the unloaded condition the arrangement is such that the synchronous'machine VII `rotates with 'the same speed as the'iiuluctionmachine. This being put, it will now be plain that an increase of load on the synchronous machine slows itdown, thus increasing the slip of the induction-machines, which carries with it the ability of the induction-machines to take a greater load, and thus-distributes the load between the syncl'n'onous machine and the induction-machines in a uniform manner. This process of 'regulating the driving of the asynchronous lportion of this specification.

v l generators in accordance with which the synchronous machine suers a greater drop in speed under increase of load than the asynchronous machine is another part of my invention.

To' the secondary of the induction machines I V, V, and VI are connected the brushes of my exciters IX, X, and XI, which need not be further described here, since they have been described at great length in a prior While there are numerous ways in which these exciters "may be driven, I have preferred to arrange on each of their shafts a small directcurrent .motor XIII, taking current .from the line XV through circuits having switches XIV. .opening these switches the exciters are stoppe and thus placed out of operation. On the ,other hand, by actuating the rheostat furnished to the same by XVIII in the line XV the speeds of the several motors XIII, and with it the speeds of the exciters to which they are connected, may be increased or decreased and varied in a suitable manner. Now to each value of the voltage of the line of the power factor of the line and the intensity of the current, Whichis one of the induction or asynchronous generators, corresponds a well-determined value of the intensity of the exciting-current which this machine re uires. It' the exciting-current furnished to t e induction-maclnne under consideration b the exciter associated therewith has some ifferi ent intensity from that actually required, a wattlesscurrent will pass from the asynchronous generator to the synchronous generator or from the synchronous generator to the asynchronous generator. All that is necessary, therefore, to prevent this passage of wattless currents between the synchronous generator and the asynchronous generators is to give such a speed to the several exciters of the asynchronous generators as will furnish the proper m agn'etization-currents' to the asynchronous machinefwith which they are connected. Bv manipulating the rheostat XVIII it will be possible to simultaneously increase or decrease the speeds of the exciters IX, X, and XI, and with it the intensity of the exciting-currents furnished by them, so that the intensity of the wattless or correction current owing between the generators will be zero. This result can always be obtained so long as the load on the generators does not muchexceed their maximum load.

The apparatus disclosed herein is covered in the parentapplication, Serial No. 140,933, iled January 28, 1903, of which this is a division.

I claim- 1. The process of producing the effect of an added negative resistance in one member of an asynchronous machine by impressing thereon an electromotive force of the frequency of the current in that member but of a phase in opposition to the voltage inserted by such current, substantially as described.

2. The process of producing the effect of an added negative resistance in any secondary circuit of an asynchronous machine by impressing thereon an electromotive force of the frequency of the current therein but of a phase in opposition to the volta e'inserted by such current, substantially as escribed.

3. The process of producing the effect of an added negative resistance 1n the secondary circuit 0I an asynchronous generator by impressing thereon an electromotive force'of the frequency of the current therein but of a phase in opposition to the voltage inserted by suchcurrent, substantially as described.

4. The process of producing the effect of an added negative resistance in the multi- IXO lIC)

phase secondary circuits of an' asynchronous machine by impressing on each circuit an electromotive force of the frequency of the current therein but of a phase in opposition to l 5 the voltave inserted by such current substan--lv ltially as described.

5. The process of regulating the actionof a synchronous generator electrically connected Kto an asynchronous sists in causing the synchronous generator to have a Greater drop in speed under increase of load than the asynchronous generator, substantially as described.

6. The 'process of running a synchronous r 5 .generator electrically connected to several generator, which con- Witnesses:

HANsoN C. Cox'n. JEAN Corrieri 

